Edited to add: One of our girls was sick and had to be separated from the group. We kept her in a wire dog kennel in the kitchen until she recovered (about 2 months). When it was time for her to rejoin the others, there was a few minutes of stare downs and posturing, then everyone went back to what they were doing. It all worked out fine.
No, it's just we'll be gone for a while and I don't want the people who will be taking care of our chickens to have to worry about the new pullet getting out of the pen, so I want to put her somewhere she can't fly out.